BRAMAH PRESS, the practical application of Pascal's law that fluids transmit pressure equally in all directions. Joseph Bramah, about 1796, was able to construct a successful press, using a small pump plunger and conducting the water to a ram of much larger area. Each portion of the surface of the ram equal in area to that of the plunger therefore receives a like pressure, the difference in the two total areas greatly increasing the ram pressure. A force of a few pounds acting on the pump lever can thus be converted into hundreds of pounds force at the ram. The hand-operated presses built on this principle are extremely numerous, for various pressing and forming processes as required in the book-binding, printing, paper, leather, tobacco, tea, drug, jewellery, engineering, and electrical trades. When a larger in stallation is required, or the powers are high, power-driven pumps are employed, or the supply is taken from accumulators or service mains. Nevertheless, hand-actuated presses can be had up to 30o tons power. Power-actuated types comprise those for punch ing and shearing, riveting, flanging, forging, and bending, baling, bundling, railway wheel forcing, and some special forms utilized in celluloid, cotton, tube, and munitions manufacture.
There are three methods now by which cost of working is lessened, by comparison with the ordinary pump or accumulator supply above mentioned. (I) Water saving ; by filling the press cylinder with ordinary supply and only turning on the pressure water at the moment of action, thus saving all the pressure water possible. (2) Fitting three cylinders for a big press and using one, two, or three according to needs, giving, for instance, either 200, 400, or 600 tons pressure. (3) Eliminating pumps and accumulators by the installation of a steam-intensifier. This con sists of a large steam cylinder the piston of which operates a small hydraulic plunger, so that, for example, 150 lb. steam pres sure can be made to give a hydraulic pressure of tons per square inch.